1. Field of the Invention
The present invention relates to a semiconductor device which has a thin semiconductor element mounted thereon.
2. Discussion of Background
When, in particular, a thin semiconductor element (having a thickness not greater than 0.1 mm for instance) is mounted on a conventional semiconductor device, a wafer is preliminarily ground to a thin one, the wafer is separated into independent chips by dicing, and the independent chips are mounted on substrates or lead frames in a usual method.
The usual method has created a problem in that a chip is likely to be fractured in handling, or that when a chip is mounted on a substrate, a stress is generated by bonding electrode portions to damage a coupling portion or the semiconductor element.
It is an object of the present invention to solve the problem, and provides a semiconductor device having a thin semiconductor element mounted thereon, the semiconductor element being obtained by mounting a plurality of chips on a substrate before thinning the thickness of the chips, and polishing rear surfaces of the chips with coupling portions protected by sealing after, e.g. testing or repairing or with a stress to the chips lessened.
According to a first aspect of the present invention, there is provided semiconductor device having a thin semiconductor element mounted thereon, the semiconductor element being obtained by mounting a plurality of semiconductor elements on a substrate, polishing rear surfaces of the semiconductor elements after sealing coupling portions, and separating the substrate with the semiconductor elements thereon into independent semiconductor devices.
According to a second aspect of the present invention, a reinforcing plate is fixed on the substrate, and the substrate with the semiconductor elements thereon are separated into the independent semiconductor devices after assembly.
According to a third aspect of the present invention, a reinforcing plate is fixed on the substrate, the reinforcing plate comprising a metallic plate and a wiring plate in layered fashion, and conduction is made between the wiring plate and wiring on the substrate.
According to a fourth aspect of the present invention, there is provided a semiconductor device having thin semiconductors element mounted thereon, the semiconductor elements being obtained by mounting a plurality of semiconductor elements, sealing the semiconductor elements, providing a laminate on rear surfaces of the semiconductor elements to form a wiring layer with the semiconductor elements included therein after polishing the rear surfaces of the semiconductor elements, and wiring, followed by repeating the same step.
The present invention is constructed as stated earlier, offering the following advantages.
In accordance with the first aspect, the plural semiconductor elements are mounted on a substrate, and the rear surfaces of the semiconductor elements are polished after sealing. As a result, the semiconductor elements can be made thin without damaging the semiconductor elements.
In accordance with the second aspect, the reinforcing plate is fixed on the substrate. Even if the substrate has low rigidity, the substrate can ensure required flatness, allowing polishing of the rear surfaces to be carried out with good precision.
In accordance with the third aspect, the reinforcing plate is fixed on the substrate, and conduction is made between the wiring plate and the wiring on the substrate. Thus, the semiconductor device can improve a wiring allowance for the substrate, can have a thin semiconductor element mounted thereon, and the semiconductor element can be made smaller.
In accordance with the fourth aspect, semiconductor elements are mounted, the semiconductor elements are sealed, a wiring layer is provided by laminating after polishing rear surfaces of the semiconductor elements, and followed by the repeating the same step. This arrangement can provide a semiconductor device with a plurality of chips mounted thereon in high density.